X-ray Computed Tomography (CT) system can reconstruct a tomographic image of an object under measurement utilizing computer technology, so as to obtain a three-dimensional (3-D) tomographic image. By transmitting a single axial plane radiation through an object under measurement, a computer acquires the penetrated radiation and generates an image by 3-D reconstruction based on the fact that the radiation absorptivity and transmittance by different parts of the object are different. CT technology is now in widespread use in various fields, such as hospital examination, industrial inspection, security inspection, air transportation, port transportation, large cargo container, etc.
As for hospital examination, the operation principle of a CT system is described as follows. Based on the fact that X-ray absorptivity and transmittance by different human tissues are different, a high-sensitivity apparatus may be used to measure a human body. Measurement data can be acquired and input into a computer for processing. Then, a tomographic or stereoscopic image of a measured position of the human body can be captured, so that a minor lesion can be detected at any position of the human body.
In practical measurements, when a human object is lying on a scanning table, a scanning table extends outside from a supporting platform and delivers the human object to a scanning plane composed of an X-ray source and a detector. The X-ray source and the detector rotate around the human object to acquire scanning data of the human object. Subject to a weight of the human subject, the scanning table may shift downwards to a certain extent with the scanning table's extending length and the human's weight, causing a nominal position of the scanning table does not conform to the actual. When the position of the scanning table does not conform to the actual, the position and profile of a tomographic image reconstructed by the CT system may shift as well, which does not conform to the expected, and in turn causes interference with medical diagnosis.
In light of the above problems, an image position compensation method is needed, so as to implement a scanning table position detection method using normal functions of an X-ray CT apparatus, where a correct tomographic image can be acquired using the image position compensation method, which thereby provides accurate image information for medical diagnosis.